Studies in the Theory of Descent, Volume II

[The following characters are given in Stainton’s “Manual of British Butterflies and Moths,” vol. i. p. 114: – “Larva of very variable form: at one extreme we find the singular Cerura larvæ, with only fourteen legs, and two long projecting tails from the last segment; at the other extreme we have larvæ with sixteen legs and no peculiarity of form, such as Chaonia and Bucephala; most have, however, the peculiarity of holding the hind segment of the body erect when in repose; generally quite naked, though downy in Bucephala and rather hairy in Curtulu; very frequently there are projections on the back of the twelfth segment.” R.M.]

16

Encyl. Meth. ix. p. 310.

17

[The genus Vanessa (in the wide sense) appears to be in a remarkable condition of what may be called phyletic preservation. Thus, the group of species allied to V. C. – album passes by almost insensible steps into the group of butterflies typified by our “Tortoiseshells.” The following is a list of some of the intermediate species in their transitional order: —I. – album, V. – album, Faunus, Comma, California, Dryas, Polychloros, Xanthomelas, Cashmirensis, Urticæ, Milberti, &c. Similarly, our Atalanta and Cardui are connected by a number of intermediate forms, showing a complete transition from the one to the other. The following is the order of the species so far as I am acquainted with them: —Atalanta, Dejeanii, Callirhoë, Tammeamea, Myrinna, Huntera, Terpsichore, Carye, Kershawii, and Cardui. R.M.]

18

“Prodromus Systematis Lepidopterorum.” Regensburg, 1864.

19

[The larva of Acherontia Morta, figured by Butler (see note 121, p. 262), possesses the characteristically recurved horn; that of Ach. Medusa figured by the same author, does not appear to possess this character in any marked degree. R.M.]

20

[See note 97, p. 233. R.M.]

21

Loc. cit. Pl. XXV. [This species is referred by Butler to the genus Paonias, Hübn. R.M.]

22

Abbot and Smith, Pl. XXIX. [Placed by Butler in the genus Cressonia, Grote and Robinson. Abbot and Smith state that this larva is sometimes green. According to Mr. Herman Strecker (Lepidop. Rhopal. and Hetero, Reading, Pa. 1874, p. 54) it feeds upon black walnut (Juglans Nigra), hickory (Carya Alba), and ironwood (Ostrya Virginica). Of the North American species of Smerinthus, the following, in addition to Excæcatus, closely resemble our Ocellatus: —S. (Calasymbolus) Geminatus, Say; (C.) Cerisii, Kirby; and Ophthalmicus, Boisd. In addition to S. (Cressonia) Juglandis, S. (Triptogon) Modesta much resembles our Populi. The larva of Geminatus, according to Strecker, is “pale green, lightest above, with yellow lateral granulated stripes; caudal horn violet; stigmata red. It feeds on the willow.” R.M.]

23

Cat. Brit. Mus.

24

[This lengthening of the true legs is mimetic according to Hermann Müller, and causes the anterior portion of the caterpillar to resemble a spider. See note 129, p. 290. R.M.]

25

[Certain butterflies appear to be crepuscular, if not nocturnal in their habits. Thus in his “Notes on the Lepidoptera of Natal,” Mr. W. D. Gooch states that he never saw Melanitis, Leda, or Gnophodes Parmeno on the wing by day, but generally during the hour after sunset. He adds: – “My sugar always attracted them freely, even up to 10 or 11 p.m.” Many species of Hesperidæ are also stated to be of crepuscular habits by this same observer. See “Entomologist,” vol xvi. pp. 38 and 40. R.M.]

26

I only make this assumption for the sake of simplicity, and not because I am convinced that the existing Rhopalocera are actually the oldest Lepidopterous group.

27

Zeitschrift für wissenschaftl. Zoologie, vol. xx. p. 519.

28

[See for instance Lubbock’s “Origin and Metamorphoses of Insects,” chap. iii.; and F. M. Balfour’s “Comparative Embryology,” vol. i., 1880, pp. 327 – 356. This last work contains an admirable résumé of our knowledge of the embryonic development of insects up to the date of publication. R.M.]

29

Are not the 4th, 11th, and 12th segments destitute of the rudiments of legs as in the larvæ of all existing saw-flies? I might almost infer this from Bütschli’s figures (see for instance Pl. XXV., Fig. 17A).

30

[The grub-formed Hymenopterous larvæ, like the larvæ of all other holometabolous insects, thus represent an acquired degenerative stage in the development, i. e. an adaptation to the conditions of life at that stage. Bearing in mind the above-quoted observations of Bütschli and the caterpillar-like form of the Terebrantiate group of Hymenopterous larvæ, the following remarks of Balfour’s (loc. cit. p. 353), appear highly suggestive: – “While in a general way it is clear that the larval forms of insects cannot be expected to throw much light on the nature of insect ancestors, it does nevertheless appear to me probable that such forms as the caterpillars of the Lepidoptera are not without a meaning in this respect. It is easy to conceive that even a secondary larval form may have been produced by the prolongation of one of the embryonic stages; and the general similarity of a caterpillar to Peripatus, and the retention by it of post-thoracic appendages, are facts which appear to favour this view of the origin of the caterpillar form.” See also Sir John Lubbock, loc. cit., pp. 93 and 95. R.M.]

31

[In the most recent works dealing with this order six groups, based on the character of the imagines are recognized, viz.: —Tubulifera, Terebrantia, Pupivora, Heterogyna Fossores, and Mellifera. (See, for instance, F. P. Pascoe’s “Zoological Classification,” 2nd ed. p. 147.) Of these groups the larvæ of the Terebrantia as thus restricted are all of the caterpillar type (Tenthredinidæ and Siricidæ), whilst those of the other groups are maggot-shaped. For a description of the development of the remarkable aberrant larva of Platygaster, see Ganin in Zeit. f. wissenschaftl. Zool., vol. xix. 1869. R.M.]

32

[For recent investigations on the structure of the thorax in Diptera, see a paper by Mr. A. Hammond, in Journ. Linn. Soc., Zoology, vol xv. p. 9. R.M.]

33

I am familiar with the fact that the two sub-orders of true Diptera, the short-horned (Brachycera), and the long-horned (Nemocera), are not sharply limited; and I am likewise well acquainted with the circumstance that there are forms which connect the two larval types. The connecting forms of the imagines do not, however, always coincide with the intermediate larval forms, so that there here arises a second and very striking incongruence of morphological relationship which depends only upon the circumstance that the one stage has diverged in form more widely than the other through a greater divergence in the conditions of life. The difficulty is in these cases aggravated because an apparent is added to the true form-relationship through convergence, so that without going into exact details the form and genealogical relationships of the Diptera cannot be distinguished. It would be of great interest for other reasons to make this investigation, and I hope to be able to find leisure for this purpose at some future period.

34

“Entwicklung der Dipteren.” Leipzig, 1864.

35

Lubbock concludes from the presence of thoracic legs in the embryonic larva of bees that these have been derived from a larva of the Campodea type, but he overlooks the fact that the rudiments of the abdominal legs are also present; loc. cit., p. 28.

36

“Für Darwin,” Leipzig, 1864, p. 8.

37

Mem. Peabody Acad. of Science, vol. i. No. 3.

38

Verhandl. Wien. Zoolog. Botan. Gesellsch. 1869, p. 310.

39

Über Ontogenie und Phylogenie der Insekten. Eine akademische Preisschrift. Jen. Zeitschrift. Bd. x. Neue Folge, iii. Heft 2. 1876. [Some remarks by F. M. Balfour on the origin of certain larval forms have already been quoted in a previous note (#cn_29) (p. 485 (#Page_485)). This author further states: – “The fact that in a majority of instances it is possible to trace an intimate connection between the surroundings of a larva and its organization proves in the clearest way that the characters of the majority of existing larval forms of insects have owed their origin to secondary adaptations. A few instances will illustrate this point: – In the simplest types of metamorphosis, e. g. those of the Orthoptera genuina, the larva has precisely the same habits as the adult. We find that a caterpillar form is assumed by phytophagous larvæ amongst the Lepidoptera, Hymenoptera, and Coleoptera. Where the larva has not to go in search of its nutriment the grub-like apodous form is assumed. The existence of such an apodous larva is especially striking in the Hymenoptera, in that rudiments of thoracic and abdominal appendages are present in the embryo and disappear again in the larva… It follows from the above that the development of such forms as the Orthoptera genuina is more primitive than that of the holometabolous forms, &c.” Comparative Embryology, vol. 1, p. 352. R.M.]

40